[CLUE-Tech] wireless ethernet industrial application

[David Anselmi]

Jim Ockers wrote:
> Hi everyone,
> 
> I thought I'd ask the group since I don't know what to do.  I
> have a requirement to develop a prototype industrial-strength
> communications system using COTS* hardware and WLAN.
[...]
> So, what should I get?  I thought I would use the Atheros chipset
> but the madwifi README says in the known problems section
> "Performance in lossy environments is suboptimal."  Also madwifi
> is beta, and might have a bunch of unknown problems.  The
> industrial environment that this system will live in is very
> "lossy."

Not quite sure what "industrial strength" means, nor "lossy".  Seems 
like you mean "a relatively high noise immunity in a noisy environment".

If that's the case and you can't get some radioheads to measure the 
environment and design an acceptable solution, you seem to be left with 
the empirical route.  Buy a bunch of cards that meet your availability 
and interoperability requirements and test the heck out them.

> We don't need super speed (I'm replacing a 115Kbps link) - 
> anything 1Mbps or faster would work.  Also, 2.4GHz is preferable 
> to 5GHz because the range is slightly better with the lower 
> frequency.

It may be that your "lossy-ness" is less for one than the other -- try 
them both.

> This is quite a bit different than trying to network a laptop
> and a PC together in an apartment, and I'm not even sure how to
> evaluate the WLAN hardware that's out there.

Not so much if you aren't doing any analysis and design work.  Both are 
"try it and see" approaches, aren't they ;-)

[...]
> PPS We might be able to get away with using any old WLAN card
> if we had an antenna array and phased-array signal processing
> hardware.

I seriously doubt that a phased-array antenna counts for COTS, even if 
it is somewhat homegrown :-)  Don't you wish you knew some guys who 
build those...  But you might be able to improve performance with a 
better antenna for the cards -- most likely you'd need PCI cards to have 
some kind of antenna connector but they do exist.  OTOH, if it has to be 
a laptop, it has to be reliable, and it has to be cheap, maybe you're 
entering the realm of "unreasonable requirements".  You know what the 
aerospace guys say: "fast, cheap, reliable; pick two".  Or as Steve 
Wright says, "You can't have everything.  Where would you keep it?"

Dave